With increasing concern regarding health, people have developed an interest in the safety of drinking water. In this study, we attempt to measure the economic benefits of tap water quality improvement through a case study on Pusan, the second largest city in Korea. To this end, we use a scenario that the government plans to implement a new project of improving water quality and apply the contingent valuation (CV) method. A one-and-one-half bounded dichotomous choice question (OOHBDC) format is employed to reduce the potential for response bias in multiple-bound formats such as the double-bound model, while maintaining much of the efficiency. Moreover, we employ the spike model to deal with zero willingness to pay (WTP) responses from the OOHBDC CV survey. The CV survey of 400 randomly selected households was rigorously designed to comply with the guidelines for best-practice CV studies using person-to-person interviews. From the spike OOHBDC CV model, the mean WTP for the improvement was estimated to be KRW 2,124 (USD 2.2), on average, per household, per month. The value amounts to 36.6% of monthly water bill and 20.2% of production costs of water. The conventional OOHBDC model produces statistically insignificant mean WTP estimate and even negative value, but the OOHBDC spike model OPEN ACCESSWater 2013, 5 1639 gives us statistically significant mean WTP estimate and fitted our data well. The WTP value to Pusan residents can be computed to be KRW 31.2 billion (USD 32.1 million) per year.

Traffic patterns in wireless sensor networks (WSNs) usually follow a many-to-one model. Sensor nodes close to static sinks will deplete their limited energy more rapidly than other sensors, since they will have more data to forward during multihop transmission. This will cause network partition, isolated nodes and much shortened network lifetime. Thus, how to balance energy consumption for sensor nodes is an important research issue. In recent years, exploiting sink mobility technology in WSNs has attracted much research attention because it can not only improve energy efficiency, but prolong network lifetime. In this paper, we propose an energy efficient distance-aware routing algorithm with multiple mobile sink for WSNs, where sink nodes will move with a certain speed along the network boundary to collect monitored data. We study the influence of multiple mobile sink nodes on energy consumption and network lifetime, and we mainly focus on the selection of mobile sink node number and the selection of parking positions, as well as their impact on performance metrics above. We can see that both mobile sink node number and the selection of parking position have important influence on network performance. Simulation results show that our proposed routing algorithm has better performance than traditional routing ones in terms of energy consumption.

-South Korea is recently under serious situation in supplying electricity with enough power reserve. A single fault of power plant at a peak-load time may lead to a total blackout for whole area connected by a single electric grid and isolated from other grids. Despite of the seriousness of blackout, however, there are scarce studies with ex-ante analysis of the economic costs from blackout. In order to evocate the seriousness, we calculate the economic costs for both industrial and household sectors with using some survey data and statistical methodologies. As a result, total economic costs are 39.23 trillion KRW (35.83 trillion KRW for industrial sector, 3.40 trillion KRW for household sector).

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In order to promote the utilization of peach fruits, we investigated the physicochemical characteristics of three different varieties of peach, namely, Wild Peach, Hikawa Hakuho, and Baekhyang, in various development stages (stone-hardening, fruit enlargement, and ripening). The peach fruits increased in length, width, and weight in the development stage. Baekhyang had the highest size among all the varieties in the development stage. The ratio of the length and width was the highest in the stone hardening stage and decreased thereafter. The hardness of the peach fruits decreased, except Wild Peach (p<0.05). The sugar content in all the varieties increased during the development stage, but the acidity decreased. The ratio of sugar and acidity increased with the progress of the development stage. The total phenolic content (TPC) was the highest in Baekhyang in the stone-hardening stage. All the varieties had the highest TPC in the stone-hardening stage, among all the development stages. No significant difference in the DPPH radical scavenging activity was observed in the fruit enlargement and ripening stage across the different varieties. The length, width, and weight of peach fruits increased, but the hardness decreased in the fruit development stage. The ratio of sugar and acidity increased, but the antioxidant capacity decreased.